1. Technical Field
The present invention relates to sensors that monitor forces during cutting and punching operations of web or sheet materials using electrical resistance strain gauges mounted on the cutting blade or punch.
2. Background Art
Monitoring of cutting forces in machine tool operations has been a common practice to determine tool wear. This is generally accomplished by applying strain gauges directly on the cutting tool or instrumenting the tool mounts. Interaction of forces does not allow the determination of the magnitude of the mutually perpendicular forces (radial and tangential for rotary motions) needed to characterize tool wear. Decoupling of these two forces by tool mount design is accomplished in U.S. Pat. No. 4,884,461 to Sawicki et al for the purpose of monitoring lathe tool wear. Film cutting processes require an extremely stiff support to maintain blade alignment, therefore force measurements via a compliant mount design is not possible. Since blade alignment and wear are indicated by the shape of the cutting force pulse as well as the magnitude, direct force measurement is desired to reduce effects of mount dynamics.